Interpretive Summary: Pear psylla is one of the most important insect pests of commercial pears in North America and Europe. Previous study showed that male pear psylla are attracted to odors from female-infested pear shoots, if the females are collected once overwintering has been completed. Here, we assessed whether females that are deep in the overwintering phase are as attractive to males as females that had completed overwintering. We showed that overwintering females were not attractive to males, whereas those which had completed overwintering did attract males. We also forced premature completion of the overwintering phase in the laboratory by exposing females to artificial long-day conditions, or by treating females with a chemical (fenoxycarb) known to prompt premature completion of overwintering. Females that were artificially induced to complete overwintering were attractive to males. The study supports earlier research showing that female pear psylla may emit a sex pheromone to attract males for mating. If so, this would be only the second account that any psyllid emits a sex pheromone.

Technical Abstract:
A previous study showed that male pear psylla, Cacopsylla pyricola (Förster) (Homoptera: Psyllidae) were attracted to volatiles from pear shoots infested with post-diapause females (Horton & Landolt, 2006). The present study tested whether diapause status of males and females affects behavioral response of males to odor sources. Assays were done using a Y-tube olfactometer. We collected male and female winterform psylla from pear orchards at regular intervals between late October (early diapause) and late February (post-diapause). Female-infested shoots were not attractive to males until the February samples, coinciding with ovarian maturation and onset of mating in the field. A second set of assays was done in which we manipulated diapause status in the laboratory either by manipulating photoperiod or by treating insects with an insect growth regulator, fenoxycarb. In the photoperiod experiments, both short-day and long-day males preferentially selected long-day (post-diapause) females if the females were paired in the olfactometer against short-day (diapause) females. Fenoxycarb-treated males preferred fenoxycarb-treated (post-diapause) females if paired with untreated (diapause) females; untreated males showed no preferences. Results support observations made elsewhere (Horton & Landolt, 2006) that male winterform pear psylla perceive and are attracted to volatile odors associated with pear shoots infested with post-diapause females.